Automatic timing control for free piston units



D. E. MEITZLER AUTOMATIC TIMING CONTRQL FOR FREE PISTON UNITS Filed Aug. 23, 1944 Aug. l7, 1948.

4 Sheets-Sheet 1 INVENTOR: xflma. w

- 17, 1943- D. E. MEITZLQER ,3

AUTOMATIC TIMING CONTROL FOR FREE PISTON UNITS Filed Aug.. 23, 1944 4 Sheets-Sheet 2 10 0 0 co n v m o INVENTOR AUTOMATIC TIMING CONTROL FOR FREE PISTON UNITS Filed Aug. 23, 1944 Aug. 17, 1948. p. E. MEITZLER 4 Sheets-Sheet 3 FIG.'3

TO TIMING CONTROL AUTOMATIC TIMING CONTROL FOR FREE PISTON UNITS Filed Aug. 25, 1944 D. E. MElTZLER Aug. 17, 1943.

4 Sheets-Sheet 4 OmN vwN Ohm ELN QB v mm Fm ovm OmN mm b m vmm mmm mmm No h v0 NQ mom NO 0 ON. #9 0 Jot-r200 EMF W muzz- -INVENTOR afimzzfw Patented Aug. 17, 1948 Aumnmcrm nnotat o -ram;-

" PiS'l lONUNIT S a Donald EL -Meitzlen.Manchester, 001111;, assignor f torUnited-v-AircraftS'Corporatibn'pEast Hartford,

nn, a c ll ma io fl This-invention relates "to the automatic I timing; 1

or the fuel injection in free-piston units;

When the' injection deviceg'is' actuated in-re-"- sponls eytopistonmovementwasby aca m on the restraining linkage; the injectionfisindependent 1 of 'the, p0sit'ion *at the innerend of its-stroke; and

tionwithrespect to; the locatipn ofthe endof-thepi stpn stroke, so that the -injection may-occur attl-iepropertime on each piston stroke.

An object of; this; invention is; to control the timingof the fuel in-jectionsothat it will occur at-f the desiredtime on each strokeindependently of i the-length-or positi'on of-the stroke:

As tlii'e quantity of -fuelinj ected into the" engine I cylinder-varies; length and position-'of the stroke ofthe piston 'als'o varies'; thus"-changin --theposition of the piston at the eIIdfoQ'the'cornpressi n stroke: A'-feature of this inventionfis-a timing controlwhich; adjusts-the tirning in-accordancewith'-change s--in the position -jof the piston at the";

end of the compress-ion stroke A featuref the -i nvention is a control- Tor auto matically adjustingthe timing in-'readihess{ -forstarting the unit. e

Other objects and advantages will be apparent from the specification; and -fclaimsganti irom th'e accompanying drawings which illustrate; anembodiment of -the invention;-

piston'unit;

Fig; 2- is a -fragmentary sectional view through} the restraining linkage'e Fig. 3 Jis-a sectional view through the injection pump and nozzle.=- 1

Fig 4 is' a diagrammatic-'view 'of; 'the fuel timQ in'gdevice and the master controls.;

The unit shown includes an engine cylinder av p at ng "p stq s l .and I I to.

which compressor pistons l 6 and .I 8 in cylinders .-and 2 2 rare e integrally ,connected. Sleeves. 2

andf 26 Iattached to the, compressor pistons com; n

plete the reciprocating piste eeve -c mmaat entw the .m r s ri etc mic eemh n ry ritfiaton :2 8

Their-"listen: assemblies are timoved;; apart--bmathe 1,

burnin'gcof Iuelv injectetin'i'it'o'tengine-z cylinder;-z l 0 v through one orsmor 911022165513 Lt Air-L compressed in the-'- ai-i spring cylii'iders oni the power stroke returns;the-pistonassemblies; The; assemblies are alvgays maint en s: 1 ax n lnqe. ac 34;;

ained ateqnafidifs'tances ffrom -the" ne e s brie i akaa iwh z s te elna which indicate's l the I outer? f end; of the 5 stroke portionalto thepiston stroke. The masterrco from the piston-assemblies and mes hingwitnuafe pinion 38 ona shaft lo'z-f 9 Intake manifold 42 =which extends i around: the compressor and engine cylinders, conducts @iI iOZ: intake'fva1ves in the heads ot the compressors cylinders through which air -alterriately: entwsif. opposite" ends "of" the eornpress'or cylinder The i: compressed; air leaves thecylinders through? discharge valves 46=,-"--also at; opposite; ends of f theftz. compressor cylinders" and passes into a central scavenge} chamber 48 j and-tend chambers 50Jand.1:'.v 52. These chambers mayfbeinterconnectedi byla ascavenge'rnanifoldfnotshowng-- Compressed gas from the: scavenge. chambersas enters engine ports 5 4 and 5 6 which are uncovei; er'edby'pistons l2 and I41atthe-endoftheipower stroke, thereby permitting; air to bebiownxthrough.z-: the-engine cylinder 1 Gas in thev engine fcylinder; is ;--discharg-ed through exhaust ports 5a i intomex-l v. haust manifold 60.: I

The positionsofthe pistons at the inner. endsz-ofgu their strokes areindicated by anxin'ner; -master.

control szs howing the 'location of the 'innertend li of the stroke and an outer iin'aster cont'rol5i64 These controls are actuatedjby rams (BBL- and, 68 turning with the .p'iniont3B @as shownin LFigsZ. Since the pinion is" oscillated directlyjrommhe pistons, the movement of.v cams 66' and Mus-pro.

trols are identical and a descriptionioftheigoute; master" control will suflice for both:

Fluidunderpressure from aicons'tant pressuregi, source entersta passages") in 'a casing. "through a conduitild p This;lpassagerintersects a-;-bore';1 ;e

adj acent its .outerend. and. a throttling screw J 8;

controls thetraterof flow into boreglm. A,v branchi. passageBB'. from passa e 19; connectswitha port 82in bore 16.- A plunger, 84winybore J6 has a groove iii-"which connects aliport -88 ;ga.lternatel v,

with port 82 or witha port' oji'i Port.,,88 isg con-ejrg nect'ed by a passage fizwto-the inner engi. ofabo fe 16.." Port 9flzis connecteduby achannel-flfi-inc ing'i'lz and inan adjacent casing 96 to, the inner; (left hand) "end of a boreisfiain casing 961 Azpiston ,in here 98 1s moved-tq the right by a te p ngv' I022, A plun er; flar xtend i throughthe pistonzand carries; onitsnproje fin outer end a 'push .rod. 10822 This rode-has.avrollerv-i. I I0 held against camiifiby a spring H2.;1 Plunger I04 has a centralpassage I I4 conne.cted. ;withspaced grooves H6 and I [8 in the plunger-i GrQove HBfaligns Y v A with ope nings lzqin'a sleeve I22 carried by 1 piston'JQQjandf groove llil 'is' at ed ta wer bri e 'a i iei les e 3' 'i as the plunger is moved to the right by the cam as the pistons approach the outer ends of their strokes.

Fluid under pressure from the right hand end of bore 16 enters the right hand end of bore 98 through a connecting channel I24, moving piston I to the left against the spring 98. As plunger I04 is moved to the right by cam 68 the groove I I8 is uncovered by sleeve I22 to permit discharge end of plunger 84 is proportional to the change in the location of the end position of the piston stroke, the pressure on the inner (left hand) end of plunger 84, which balances the pressure on the outer end, must vary in the same manner. In this way the pressure in the discharge conduit I26 is proportional to the spacing of the actual end of the piston stroke from the extreme outer position of the piston, and changes in pressure in' this conduit will be proportional to changes in the outer end position of the piston stroke. This pressure and change in pressure may indicate on a gauge. I28 the exact position of the end of the piston stroke and may be used for controlling the adjusting means which are used for varying the operating characteristics of the unit. I

The outer end of plunger I04 may reciprocate in a chamber I30 having an outlet conduit I32 connected to a sump, not shown. The inner end of bore 98 may be connected by a conduit I34 to the conduit I32. The inner'master control operates in a similar way and controls the pressure in discharge conduit I36 in proportion to the spacing of the actual inner end of the piston stroke from the extreme inner end position. A

bellows I38 for the inner master control and a similar bellows, not' shown, for the outer master control may minimize surges in the controls.

The inner master control is used in adjusting the timing of the fuel injection system. This system is shown as the accumulator type of fuel injection system, one example of which is described in the copending application of Meitzler, Serial No. 486,623, filed May 11, 1943, now Patent #2,405,043, July 30, 1946. For the purpose of'this application, it is sufficient'to note that fuel under pressure entering a port I40 in a casing I42 passes through a filling port I44 into the end of a bore I46 in a casing I48 in which a plunger I50 reciprocates. The end of this bore communicates through a passage I52 in a cap I54 and a conduit I56 with the injection nozzleISB.

Pump plunger I50 has a helical shoulder I60 which by covering port I44 controls the quantity of fuel delivered to the injection nozzle for each injection. The quantity may be adjusted by turning the plunger angularly by means of arack I62 engaging a pinion I64 having a sliding connection with the plunger. The plunger may be reciprocated from a cam I65 on the same shaft 40 as cams 66 and 68, the plunger moving upward during the compression strokeof the engine pistons.

. The injection nozzle I58 includes a housing I66 having a portion adapted to engage a bore in the 1 wall of the'engine cylinder. A sleeve I60 fits within the hollow housing and at the inner end is reduced in diameter to define a delivery port I10 through which fuel is discharged into the engine cylinder. A cap I12 engages the opposite end of sleeve I68 and is clamped within housing I86 by a threaded ring I14. Sleeve I68 forms an accumulator chamber I16-in which; fuel is accumulated under pressure in readines's'for injection.

Within chamber I16 is an accumulator valve including a plunger I18 having a valve element I at one end engaging a valve seat I82 in sleeve I66 for closing delivery port I10. This plunger is normally held against seat I82 by a coil spring I84 surroundingthe plunger and extending between a flange I86 on the plunger and cap I12. PlungerIlB, is slidable within sleeve I68 and has a groove I08 to permit a flow of fuel from chamber I16 to discharge port I10.

nel I98 in cap I12 permits the flow of fuel f1*ompassage I00 into the accumulator chamber. Channel I98 has a check valve 200 to prevent escape of fluid from chamber I16.

During delivery of fuel under pressure to the accumulator chamber, the pressure acting on valve element I94 assists spring I84 in holdingthe plunger against seat I82. Upon'a drop in pressure in passage I90, the pressurewithin the accumulator chamber causes the plunger to move endwise to engage-seat I92 and to open delivery port I10 for injection of fuel fromthe chamber into the engine cylinder.

An automatic timing device 202 Which is re-- ing 208. The lower end of rod 206carries a bearing shoe 2I0 engaging with a wedge 2I2 pivoted on a block H4. The other side of the wedge shaped cam 2I2 engages a bearing shoe 2I6 on the end of a reciprocating rod 2 I 8.-

The lower endof rod 2I8 engages plunger 220 reciprocating in a bore 222 in. a casing 224 mounted on housing-208. This casing has an inlet port 226 connected to conduit 204. A discharge port 228 in casing 224 is in a position to be connected with said port by a groove 230 in the plunger as they latter is moved downward during the compression stroke of the engine pistons.

Venting of conduit 226 when ports 224 and 288" are connected causes injection of fuel by a in pressure in conduit 204.

The point at which injection takes place is adjusted by endwise movement of wedge 2I2 between the bearing shoes and this is accomplished by means of. a servo-motor. As shown, block H4 .is mounted on a piston rod 232 extending from a piston 234 in a bore 236 in a housing 238. Fluid under pressure from a constant pressure source is alternately directed to opposite ends of bore 236 by a sliding valve 240 in a parallel bore 242.

. Fluid under pressure enters bore 242 through a centrally located port 244 and is directed selecentrances tivel'y 'to either end cfrborefl afiithrough penny-246st and 248 extending between theaboresv: Valve=-24lt 3 plunger 252 in a bore 254 -also;in;housing 238- This plungenhasa projecting rod .connected to one end of alever 25'6,the other 'end of which is pivotedpmthe end of a rod extending from plunge: 811 234.]. Lever 256 is also connected between-fits" ends to a projectin .fikfimmnmahzegfln so that movement of plunger-" 252mmeither direction causesea corresponding but. shorter movementrof' the.val ve 240,1

Plunger 2 5.2; is .normallyi movedtoL-the right; by fluid pressure from the inner master control entering the left hand end of the bore and moving the plunger against the action of a spring 258. As the pressure from the inner master control increases, indicating that the actual inner end of the piston stroke is moving away from inner dead center, the wedge 2 I2 is moved to the left to cause uncovering of port 226 and thereby to cause injection of fuel at a point farther from inner dead center. Conversely, as the actual inner end of the piston stroke approaches inner dead center the injection occurs at a point nearer to inner dead center by movement of wedge 2I'2 to the right.

As shown, conduit I36 connects the pressure delivery port of the inner master control to a port 262 in housing 238. This port intersects a bore 264 in which a valve plunger 266 is slidable. This valve has a groove normally connecting port 262 to a passage 268 from this bore to the left hand end of bore 254. Plunger 266 is normally held in the position shown by a spring 210.

During normal operation, a channel 212 connects the ends of bore 242 to the right hand end of bore 254 and other channels 214 connect the right hand end of this bore and the left hand end of bore 264 to a vent conduit 216. The timing device is thus responsive to changes in the pressure from the inner master control, so that the injection occurs in predetermined relation to the actual inn-er end of the piston stroke.

This device may operate under substantial variations in atmospheric pressure, especially when used in an aircraft power plant. The operation of the device will not be adjusted by atmospheric changes and no altitude compensation will be necessary, since both the automatic timing device and the master controls are vented to atmospheric pressure. That is, conduits I32 and I34 vent the master control, and conduit 216 with the connecting passages in casing 238 vent the timing device.

In starting the unit, the piston assemblies are moved to starting positions spaced from the inner dead center positions. This results in a high pressure from the inner master control which would normally advance the timing as far as possible. If this is undesirable, the outer master control may be used to set the timing for starting.

For this purpose, conduit rzs from the outer master control, connects with the lower end of a bore 218 for a plunger 28!]. This plunger, which acts as a relay, is normally held in the position shown by a spring 282 and is moved against the pressure of this spring when the outer master control pressure reaches the high value resulting from the starting position of the piston. Plunger 280 uncovers a passage 284 from bore 218 to the right hand end of bore 264. Pressure 6i; entering i'th'e end inf-choret264-= moves iplungen 2 66, 5 to'the left' .andn connectschannel 268 iwithifaivenea channeli 28li therebydropping. tlfepressureeatvi the-left"handcendi of plungen=252 Gand" causing a ,.wedge M2 to be withdrawn to its-extremetright handipositiunsas detemnnedeby amut: 288;;bn .:rod 232szengag-mgxzai projecting-r: lug-12flfinonahousinge; 2383i Aftenzthmunitnstantszand:the outenonaster control.pressure-zistreducediithecplungers 2.6.6:aand... =28mreturn toztheupositionszzshown :andithe injecew tion timingnissthen adjustedizbyethe innenrmaster-re controhipl-w x r a v a It'siszto be'understoodithatztherinvention is non;

limitedrtc nonspecific .embodimentaherei-n illllS-iyi itr-atcd eandirdescrib ed, abutnnay.doetused inr others waysewithdutsdeparture fromsits;spiiitxasudefinede by the following claims:

I claim:

1. A free-piston unit including a cylinder, a piston reciprocating in the cylinder and having a variable length of stroke, and means for injecting fuel into the cylinder, in combination with means for automatically adjusting said fuel injecting means for controlling the time of the injection of fuel with respect to the end position of the piston stroke, said adjusting means being responsive to changes in the end positions of successive strokes.

2. A free-piston unit including a cylinder, a piston reciprocating in the cylinder and having a variable length of stroke, and means for inj cting fuel into the cylinder, in combination with means associated with said injecting means and responsive to changes in the end position of the piston stroke for automatically adjusting said fuel injecting means for controlling the time of the injection of fuel with respect to the end of the piston stroke.

3. A free-piston unit including a cylinder, a piston reciprocating in the cylinder and having a variable length of stroke, and means for injecting fuel into the cylinder, in combination with means for automatically causing injection of fuel by said means when the piston is at a predetermined distance from the end of the compression stroke, said last means including a device responsive to changes in the inner end positions of the piston strokes and means responsive to said device for adjusting said fuel injecting means.

4. A free-piston unit including a cylinder, a piston reciprocating in the cylinder and having a variable length of stroke, and means for injecting fuel into the cylinder, in combination with means for adjusting said fuel injecting means for controlling the time of injection, said adjusting means being responsive to changes in the end position of the compression stroke of the piston.

5. A free-piston unit including :a cylinder, a piston reciprocating in the cylinder and having a variable length of stroke, and means for injecting fuel into the cylinder, including an injection plunger reciprocatedin response to piston movement, in combination with means for procuring injection by said means independently of the position of the plunger, and means for adjusting said procuring means in response to change in the end position of the piston strokes.

6. A free-piston unit including a cylinder, a piston in the cylinder and having a variable length of stroke, and accumulator injection means for injecting fuel into said cylinder, in combination with means for timing the injection of fuel by said means with respect to the end position of the piston at the end of the compression stroke,

2,447,352 7 8' said'timing means including a device responsive curing said drop in pressureindependently of the to changes in the end positions-of the piston posi'tion-of'the plunger. strokes, and means actuated by said device for V DONALD E. MEITZLER. adjusting the timing of the fuel injection by said injection means. 5 REFERENCES CITED A free-P1517011 t including cylinder, The-following references are of record in the piston in the cylinder and having avariablelength file of t patent; of stroke, and accumulator injection means for injecting fuel into said cylinder, including a. UNITED STATES PATENTS ofthe compression stroke of the piston for pro- 509,111 Great Britain July 11, 1939 plunger adapted .to pump fuel into an accumu-' 10 Number 'Name Date l'ator chamber, a nozzle, and a valve movable in 2,178,311 Peso-ara Oct. 31, 1939 response to a drop in pressure between said chamher and plunger to connect said chamber to the FOREIGN PATENTS,

nozzle for injection of fuel, in combination with Number Country 1 I Date means responsive to changes in the end position 15 210,884 Switzerland Aug. 15, 1940 

